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The surface of GCr15SiMn bearing steel was strengthened by supersonic fine particle bombardment (SFPB), and the effects of different impact times on the microstructure, mechanical properties and friction and wear properties of the material were studied. The results show that the surface roughness of GCr15SiMn steel samples increases and the grain is refined after SFPB. As the impact time prolongs, the grain size gradually decreases. When the bombardment time is 180 s, the surface grain size of the sample reaches 12.7 nm. The microhardness of the sample gradually increases and tends to stabilize with the increase of the impact time. The residual compressive stress layer is produced on the surface of the sample after SFPB and the residual compressive stress shows a trend of first increasing and then decreasing with rising the impact time. The friction coefficient and wear rate of GCr15SiMn bearing steel decreases after SFPB. The wear mechanism of the sample changes from mixture of adhesive wear and oxidation wear, accompanied by slight abrasive wear (before SFPB) to the abrasive wear, supplemented by adhesive wear (after SFPB). The wear resistance is improved by the of the grain refinement and the formation of a high residual compressive stress layer.

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The contact impact and contact stress on the tooth surface of elliptic gears are difficult to obtain, and the theory of dynamic performance analysis is not perfect, which seriously affects the widespread application of elliptic gears. To overcome the research difficulties and technical bottlenecks mentioned above, this article focuses on the dynamic meshing process of elliptic gears. Based on the theory of contact dynamics and the physical model of elliptic gear transmission, a finite element analysis method is proposed to solve the impact collision problem of elliptic gears. An accurate elliptic gear pair model was established by simulating the generation of elliptic gears by gear shaping cutters. On this basis, a finite element model for load-bearing contact and a numerical calculation model for contact stress of elliptic gears were proposed and established. The distribution patterns of contact stress, impact stress, impact resultant force, and impact time of elliptic gears were studied. The results indicate that the contact stress on the tooth surface is more sensitive to eccentricity, tooth width, and torque. The distribution of impact stress, impact resultant force, and impact time varies with the position of the gear teeth on the pitch curve. The research results can lay a theoretical foundation for the formation of the theory of elliptic gear meshing impact. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of cooperative guidance for multiple flight vehicles, comprising a leader and seeker-less followers. All the flight vehicles are required to hit the target simultaneously at a desired impact time, even though the target information is unavailable to the followers. To achieve this, a fixed-time convergent guidance law is proposed for the leader, incorporating impact time control. We introduce an adaptive cooperative guidance strategy for the seeker-less followers through coordinated position location relative to the leader. The simulation results validate the effectiveness satisfactorily coinciding with the theoretical analysis. • A three-dimensional cooperative guidance law with impact time control is presented for one leader and the other seeker-less followers. • The cooperative guidance law for the followers is achieved by leveraging the leader as a baseline and employing position coordination. • An adaptive law is given to tackle the influence of uncertainties, wherein the compensation action is exerted by the adaptive term with fractional power to achieve the finite-time convergence. [ABSTRACT FROM AUTHOR]

The increasing mortality rate in bike-related road accidents due to head injuries necessitates stronger helmets. This paper presents a cost-effective machine setup to evaluate helmet behavior during impacts. By employing unique methods to measure impact duration and post-impact energy absorption, this project eliminates the need for high-speed cameras. The results indicate that the developed machine enables scenario-based impact tests directly on helmets, providing valuable insights into collision effects. Validation confirms its effectiveness. The low-cost impact testing machine offers a practical solution for studying helmet performance and addressing the rising concerns surrounding bike accidents. [ABSTRACT FROM AUTHOR]

In this paper, based on terminal sliding mode control (TSMC), a cooperative impact time and angle constrained guidance (CITACG) law for multi-missile system with switching network topologies is proposed. The obtained CITACG is composed of two parts. One part is designed to make the missiles intercept the target from their predetermined impact angles. And the other part’s goal is to make the multiple missiles intercept the target simultaneously without predefining a common impact time. Sliding mode surface of the first part is designed based on TSMC, meanwhile integral terminal sliding mode control (ITSMC) and graph theory are applied to derive the second part of the CITACG. When the communication network switches between the connected topology and the disconnected one, a Lyapunov candidate function is introduced and the corresponding stability conditions are derived. The proposed guidance law is the summation of the two guidance parts, therefore it is a direct method and do not have to switch the guidance command between the impact angle constrained guidance law and the impact time constrained guidance law. The predetermined common impact time is not required in the proposed CITACG, and the missiles can automatically adjust themselves to intercept the target simultaneously by communicating between their neighbors. Numerical simulations demonstrate the great performance of the proposed guidance law. [ABSTRACT FROM AUTHOR]

This paper proposes integrated guidance and control for skid-to-turn cruciform canard-controlled interceptors for controlling impact time along with interception of non-maneuvering targets. This approach circumvents the possible difficulties associated with designing guidance and control subsystems independently. An interceptor control surface deflection for achieving appropriate lateral acceleration to achieve the guidance objectives are derived using sliding-mode control considering nonlinear engagement dynamics, thereby remaining effective even for engagement with large initial heading errors. The switching surface is chosen to be a function of time-to-go and its rate with different time-to-go estimates against stationary and moving targets. The time-to-go estimate for stationary target accounts for the heading angle errors, while that for constant velocity target provides an exact value. Unlike many of the existing strategies, the proposed approaches enable the interceptor to achieve an impact time, even less than its initial estimates. The efficacy of the proposed guidance strategies is validated through numerical simulations for various initial engagement geometries. Furthermore, the performance of the proposed integrated guidance and control approach is also compared with the separate design of guidance and control subsystems, and shown to be superior. [ABSTRACT FROM AUTHOR]

This paper proposes a closed⁃loop homing guidance law with the constraints of the impact time and angle for the intercepting a constant⁃velocity target. In order to achieve the required terminal constraints，the line⁃of⁃sight （LOS） profile of the missile is modeled as a polynomial with one tuning parameter that is selected via an online optimization routine. Then，a terminal sliding mode guidance law is developed to nullify the tracking error within a fixed time. The key feature of the proposed guidance law is that it does not require the information of time⁃to⁃go estimation and the predictive intercept point. Numerical simulations are conducted to demonstrate the effectiveness and robustness of the proposed guidance law. [ABSTRACT FROM AUTHOR]

Considering the problem that the optimal error dynamics can only converge at the terminal time, an impact angle/time constraint missile guidance law with finite-time convergence is designed in this paper, which is based on the pure proportional navigation (PPN) guidance law and the fast terminal error dynamics (FTED) approach. The missile guidance model and FTED equation are given first, and the dynamic equation of impact angle/time error based on PPN is also derived. Then, the guidance law is designed based on FTED, and the guidance error can converge to 0 in a finite time. Furthermore, considering the field of view constraint, the guidance law is improved by using the saturation function mapping method. Finally, a numerical simulation example is given to verify the effectiveness of the guidance law, which shows that the guidance law proposed in this paper can make the missile quickly adjust to the desired states in advance, and effectively relieve the overload saturation pressure of the actuator. [ABSTRACT FROM AUTHOR]

The increasing mortality rate in bike-related road accidents due to head injuries necessitates stronger helmets. This paper presents a cost-effective machine setup to evaluate helmet behavior during impacts. By employing unique methods to measure impact duration and post-impact energy absorption, this project eliminates the need for high-speed cameras. The results indicate that the developed machine enables scenario-based impact tests directly on helmets, providing valuable insights into collision effects. Validation confirms its effectiveness. The low-cost impact testing machine offers a practical solution for studying helmet performance and addressing the rising concerns surrounding bike accidents.

In order to improve the penetration ability of missile and attack the target effectively, the guidance law realizing the control of both impact time and impact angle is studied. Based on a data-driven method, the guidance process is divided into the first stage of impact time control and the second stage of impact angle control. The driving data is generated according to the guidance law of impact angle control, and the mapping network of time to go is established by using artificial neural network technology to obtain the error of impact time in the impact time control stage. Based on the proportional guidance method, the impact time control guidance law is designed with the error of impact time, so that the missile can control the impact time and the impact angle simultaneously. The simulation results show that the proposed guidance law can effectively control the impact time and impact angle under different conditions. Compared with existing literature, the maximum overload is reduced by about 43%, and the total control energy required is reduced by about 46%. [ABSTRACT FROM AUTHOR]

Spiker–blocker encounters are a key moment for determining the result of a volleyball rally. The characterization of such a moment using physical–statistical parameters allows us to reproduce the possible ball's trajectory and then make calculations to set up the defense in an optimal way. In this work, we present a computational algorithm that shows the possible worst scenarios of ball trajectories for a volleyball defense, in terms of the covered area by the block and the impact time of the backcourt defense to contact the ball before it reaches the floor. The algorithm is based on the kinematic equations of motion, trigonometry, and statistical parameters of the players. We have called it the Attack-Block-Court Defense algorithm (the ABCD algorithm), since it only requires the 3D-coordinates of the attacker and the blocker, and a discretized court in a number of cells. With those data, the algorithm calculates the percentage of the covered area by the blocker and the time at which the ball impacts the court (impact time). More specifically, the structure of the algorithm consists of setting up the spiker's and blocker's locations at the time the spiker hits the ball, and then applying the kinematic equations to calculate the worst scenario for the team in defense. The case of a middle-hitter attack with a single block over the net is simulated, and an analysis of the space of input variables for such a case is performed. We found a strong dependence on the average impact time and the covered area on both the attack–block height's ratio and the attack height. The standard deviation of the impact time was the variable that showed more asymmetry, respecting the input variables. An asymmetric case considering more variables with a wing spiker and three blockers is also shown, in order to illustrate the potential of the model in a more complex scenario. The results have potential applications, as a supporting tool for coaches in the design of customized defense or attack systems, in the positioning of players according to the prior knowledge of the opponent team, and in the development of replay and video-game technologies in multimedia systems. [ABSTRACT FROM AUTHOR]

In this article, a sliding mode control–based nonlinear guidance scheme for controlling both impact angle and impact time simultaneously is proposed. The problem of impact angle control is first transformed to that of controlling line-of-sight angle and its rate, while the requirement of impact time is achieved by tracking the desired time-to-go. The chosen time-to-go estimate accounts for the curvature required to meet the impact angle requirements toward the target interception. In order to satisfy both of these terminal constraints, the sliding surface is defined as a combination of impact time error and the variable pertaining to the errors in line-of-sight angle and its rate, with appropriate gains assigned to them. The interceptor first performs necessary maneuvers to meet the impact time requirements and then steers its course to achieve the target interception at a desired impact angle. The guidance law is initially derived using nonlinear engagement kinematics against stationary targets and then extended to cater to constant velocity targets using the concept of predicted interception point. Numerical simulations are performed to validate the efficacy of the proposed guidance scheme for various initial engagement geometries. The performance of the proposed guidance scheme is also compared with those of the existing guidance laws and shown to be superior. [ABSTRACT FROM AUTHOR]

In this article, impact time and angle constrained guidance law is proposed using a range‐based line‐of‐sight (LOS) shaping strategy. The relative motion of missile and target is described in a polar coordinate, where the LOS angle can be shaped as a polynomial function of range‐to‐go. The order of the polynomial function is selected according to the number of constraints. Coefficients of the polynomial function are determined by the boundary conditions and solved through a simple integral equation, which facilitates the onboard implementation. Guidance command is designed in a state feedback form to track the shaped trajectory. The proposed guidance law shows some advantages over several similar polynomial shaping based guidance laws. Multiple simulation studies demonstrate the effectiveness of the proposed guidance law. [ABSTRACT FROM AUTHOR]

Based on adaptive sliding mode control method, this paper considers the interception problem to deal with both impact time and angle constraints. The stability and convergence characteristic of proposed guidance law are analyzed. The requirements of the terminal constraints and minimum miss distance can be satisfied. An adaptive law is put forward to adjust the guidance gain. The simulation results indicate that the missile with proposed guidance law can intercept the target successfully with not only desired impact time but also expected impact angle. The interception task can be fulfilled in a satisfactory manner.

This article proposes a guidance strategy that enables the interceptor to control its impact time against stationary targets, while also meeting the field-of-view (FOV) constraints of the on-board seeker. The guidance strategy, so designed, always keeps the target within its FOV using its seeker. A barrier Lyapunov function is used to meet the FOV constraints, and an approximate expression for the interceptor's lead angle is obtained analytically. This facilitates the computation, as well as control, of impact time. The proposed guidance consists of two stages, with the former stage being deviated pursuit, while during the latter stage, the deviation angle or lead angle decreases to zero. This, in turn, ensures a zero terminal lateral acceleration. Furthermore, through a cooperative selection of tuning parameters, simultaneous interception of the target by multiple interceptors (also called salvo) can be achieved. Simulations, that are run for different engagement scenarios and with varying tuning parameters, vindicate the efficacy of the proposed strategy. [ABSTRACT FROM AUTHOR]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this article, two cooperative guidance schemes with impact angle and time constraints are proposed for multiple missiles cooperatively intercepting a maneuvering target in the presence or absence of a leader missile. First, cooperative interception with impact angle constraint is formulated based on the relative motion equation between the interceptors. Subsequently, the design of the guidance law is divided into two stages. In the first stage, based on finite-time consensus theory and the super-twisting control algorithm, the cooperative guidance law in the direction of the line of sight (LOS) is derived to control the impact time so that all missiles can simultaneously intercept the target in finite time. Then, based on finite-time sliding mode control and the super-twisting control algorithm, a finite-time convergence cooperative guidance law in the normal direction to the LOS is developed to control the intercept angle and the LOS angle rate so that each missile can accurately hit the target at a desired angle. Finally, by controlling the consensus error of flight time in the presence of a leader missile, a finite-time cooperative guidance method in the “leader–follower” scenario is derived for simultaneous arrival at the target. The proposed methods can effectively suppress chattering and ensure fast convergence in finite time. Simulation experiments are conducted to verify the effectiveness of the proposed cooperative guidance schemes. [ABSTRACT FROM AUTHOR]

The mission of simultaneous attack and warhead lethality enhancement requires the constraints on impact time and angle in the guidance design. To this end, a two-stage guidance law considering constrained impact as well as the robustness against external disturbances and heading errors is proposed. The first stage is based on a circle involute geometrical rule that guarantees the desired velocity direction at the involute's end. With this goal achieved, the involute guidance is switched to the guidance of nullifying line-of-sight rate such that near-zero maneuver in the second stage is ensured. To achieve both impact time and angle constraints, a simple parameter determination approach is provided to find explicit solutions for the desired two-stage trajectory. Meanwhile, a robust two-stage guidance law is constructed to implement the geometrical rule, guarantee terminal constraints, and ensure robustness. The proposed technique is easy to implement, in that it does not involve model linearization, time-to-go estimation, and numerical optimization routine. Additionally, the achievable range of different constraints is analyzed considering practical issues such as initial launch angles, initial line-of-sight angles, and acceleration limits. Extensive simulations are carried out in various engagement scenarios under uncertainties and disturbances to validate the effectiveness and robustness of the proposed guidance law. [ABSTRACT FROM AUTHOR]

This paper addresses a novel impact time and angle control guidance law using a Bézier curve. The 2nd order Bézier curve consists of one control point and two boundary points; initial point P0, middle point P1 and end point P2. The curve is tangent to the line P0-P1 and the line P1-P2, respectively, and always exists in the convex hull of the control points. Proposed Bézier curve navigation guidance, makes the missile follow the Bézier curve with the feedback form of guidance command so that the missile hits the target on the desired time in the desired direction. We conducted numerical simulations on several terminal conditions to demonstrate the performance of proposed method.

A cooperative salvo guidance strategy using fixed finite-time consensus is proposed here. The consensus algorithm is based on sliding mode control. The cooperative salvo attack problem is transformed to a consensus problem over a cycle digraph. This aids in designing a guidance strategy through selection of heterogeneous gains. The proposed strategy guarantees convergence to a common impact time for all the interceptors, within a fixed time, from a wide range of initial heading angles. Subsequently, the guidance strategy is extended to cooperatively intercept a constant velocity target. The efficacy of the proposed algorithm is vindicated through simulations on both stationary and constant velocity targets. Numerical simulations are also performed on realistic missile models that account for aerodynamic parameter variations, yielding satisfactory performance. [ABSTRACT FROM AUTHOR]

Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A novel two-stage missile guidance law for impact time and angle control is proposed. This guidance law is derived based on the nonlinear engagement dynamics without using small angle assumption. In order to control both impact time and impact angle, a two-stage scheme is developed. This scheme is composed of a nonsingular sliding mode guidance law for the first stage and a switching target strategy for the second stage. The guidance law is switched from the first stage to the second stage when the switching condition is attained, which can ensure that the guidance law is switched at the right time to satisfy impact time constraint. The switching target strategy in the second stage can achieve impact angle control with high accuracy. Impact time and angle can be controlled simultaneously under this two-stage scheme. Numerical simulations are performed to demonstrate the performance of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a guidance strategy, which caters to both impact angle and impact time terminal constraints. This guidance scheme is based on switching between impact time and impact angle guidance laws. Unlike the existing impact time guidance laws, the proposed guidance strategy takes into account the curvature of the trajectory due to requirement of impact angle. The guidance law is derived using sliding mode control theory with the switching surface based on impact time error. The interceptor first corrects its course to nullify the impact time error and then aims to achieve interception with desired impact angle. In order to reduce transitions between the two guidance laws, a novel hysteresis loop is introduced in the switching conditions. The guidance law is initially designed for stationary targets, and later it is extended to constant velocity targets using the notion of predicted interception point. In order to validate the efficacy of the proposed guidance strategy, simulation results are presented with constant as well as realistic time-varying speed interceptor models for different engagement scenarios against stationary and constant velocity targets. The performance of the guidance law is evaluated under noisy measurements and the presence of system lag and its performance is compared with other existing guidance laws. [ABSTRACT FROM AUTHOR]

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The authors propose an autopilot based on partial integrated guidance and control for missiles to achieve interception at a pre‐specified impact angle and a close approximation of impact time. The scheme has an outer loop comprising the engagement model and slow dynamics (to generate a pitch‐rate command that causes the missile to establish a collision course with the target), and an inner loop comprising the fast dynamics (to make the pitch rate track its command signal). The authors divide the missile flight into two phases; in the first phase the controller causes the missile line‐of‐sight (LOS) angle (impact angle) to converge to the pre‐specified value at a pre‐specified time, and to remain there thereafter (and hence establishes a collision course at the desired impact angle). In the second phase, the missile will fly along the LOS until interception occurs. The authors also provide an estimated calculation of the impact time and give the factors that influence the estimate, which helps the user systematically choose the missile parameters in order to achieve a certain impact time; this result can be applied to the case of salvo attack of multiple missiles without online data links. Finally, simulations are performed to verify the scheme effectiveness. [ABSTRACT FROM AUTHOR]